During the preparation of integrated circuit modules, input/output (I/O) pins are inserted into a substrate. The input/output pins provide the needed electrical connections to the integrated circuit chip or chips which are subsequently connected to the substrate or carrier. The integrated circuit chips are attached to the integrated circuit substrate or carrier by applying solder to preselected areas on the substrate which is generally referred to in the art as the "chip pad area". Such areas can be defined, for instance, by providing preselected exposed areas of a metal which will accept the solder, such as copper. In addition, a solder flux composition is normally applied to the substrate to facilitate the application of the solder to the chip pad area. After solder is applied to the chip pad area, any flux and/or flux residue is removed prior to attaching the integrated circuit chip so as to provide as clean a module as possible.
After attachment of the integrated circuit chip(s) and subsequent flux residual removal, a top seal coating composition is applied to the integrated circuit module in order to protect the top side of the module which contains the integrated circuit chip from corrosion and/or electromigration.
Top seal compositions are employed in order to prevent failure of the substrate and device due to corrosion; to immoblize conductive particles; to extend the thermal fatigue life of the solder interconnection between the substrate and chip; and to act as a protective barrier for alpha particle sensitive semiconductors. However, the top seal compositions which are now commercially employed, although for the most part, satisfactory, do not provide all of the above desirable functions to a satisfactory degree. For instance, the top seal compositions now employed provide satisfactory levels of at most three of the above functions. Accordingly, depending upon desired use of the integrated circuit module, one or more of the above functions is normally compromised by the selection of the particular top seal composition employed. One of the more common types of top seal compositions employed is obtained from curing a composition containing as the binder a polyamide-imide.
In addition, the top seal composition must possess the type of flow characteristics needed to coat the solder pattern in a reliable and controllable manner.